WikiLeaks founder Julian Assange has lost his appellate bid to bar his extradition to Sweden to face questioning about an alleged sexual assault.

Two appeals judges in London said the case involved allegations of “serious sexual offenses” and upheld a ruling that Assange should be extradited, according to the Associated Press, the New York Times and the Guardian. The court said Assange’s extradition was not disproportionate since the allegations were serious.

The Times cites an anonymous source who says Assange will seek an appeal before Britain’s highest court. He has not been charged in Sweden, but he would face questioning there. He previously has criticized the country’s strict sex crimes laws.

To win the right to appeal, Assange will have to persuade the high court there is a greater issue of public importance that should be addressed, the Guardian says.